1. Field of the Invention
The present invention relates to an illumination apparatus and a projection apparatus having it and, more particularly, to the illumination apparatus that is compact and that can implement highly uniform illumination, which is suitably applicable, for example, to color liquid-crystal projectors of a three panel type.
2. Related Background Art
In recent years, the illumination apparatus in the field of liquid-crystal projectors employs an illumination system using a fly""s eye lens or a rod type integrator in the optical path in order to realize high luminance and enhance uniformity of screen illuminance, and one of such apparatus is proposed, for example, in Japanese Patent Application Laid-Open No. 7-98479.
FIG. 10 is a sectional view of the major part of the illumination system in a conventional, color liquid-crystal projector of the three panel type. In FIG. 10, DM1 designates a red-transmitting dichroic mirror. DM2 denotes a blue-transmitting dichroic mirror. G1, G2, and G3 represent lenses, these three lenses composing a blue-path relay lens group 76B. RLCD indicates a liquid crystal display device for red only, GLCD that for green only, and BLCD that for blue only.
Rays from a light source 71 are reflected by a reflector 72 to be outgoing from the reflector 72 in the form of parallel rays. Then the rays are incident to a first lens array 73 to be separated into a plurality of beams by the first lens array 73. The plurality of beams form a plurality of secondary light source images (which are images of the light source 71) on a second lens array 74. Light from each secondary light source image formed on the second lens array 74 is guided through a PBS element 75 to be subjected to polarization conversion. After that, the light travels via a condenser lens 76, a trichromatic separation system (DM1, DM2), and a field lens 76R or 76G, or the relay lens group 76B placed immediately before the liquid crystal display device (RLCD, GLCD, or BLCD), whereby an optical conjugate relation is maintained between the light entrance plane or the principal plane of each lens unit forming the first lens array 73, and the liquid crystal display devices (i.e., the image on this plane of each unit lens is formed on the display devices), thereby realizing superimposed illumination in a rectangular shape matched with the shape of the liquid crystal display devices.
FIG. 10 showed the example of the illumination system using the lens arrays (73, 74), but there is also another illumination system with the rod integrator contemplated. Specifically, the light from the light source 71 is made incident as convergent light to the rod so as to form a light source image on the light entrance plane of the rod, and a plurality of secondary light source images (images of the light source) are formed from the light source image formed on the light entrance plane, by total reflection on the side surfaces of the rod integrator and by a lens unit placed thereafter. After that, the light from each of the secondary light source images is guided through the PBS element to effect polarization conversion thereof. Then the light travels via the condenser lens 76, the trichromatic separation system (DM1, DM2), and the field lens or the relay lens group placed immediately before each liquid crystal display device, whereby the aforementioned optical conjugate relation is maintained between the light exit plane of the rod integrator and the liquid crystal display devices, thereby realizing the superimposed illumination in the rectangular shape matched with the shape of the liquid crystal display devices.
In the illumination systems of the two types described above, where a cross dichroic prism 78 is used as a color composition system, the surfaces of the three-color liquid-crystal display devices, which are conjugate planes (i.e., planes in the optically conjugate relation, i.e., in the image forming relation) with a screen surface, need to be placed at nearly equal distance while being the length of the back focus of a projection lens 77 apart therefrom with the cross dichroic prism in between. At this time, only one out of the three color (R, G, B) beam paths having their respective wavelength zones different from each other is extended as illustrated in FIG. 10, when compared with the other two paths, and through the extended optical path the conjugate plane of the first lens array 73 or the light exit plane of the rod integrator is imaged on the liquid crystal display device, using the three relay lenses G1, G2, G3. This realizes the illumination effect equivalent to that by the two optical paths of the other colors.
However, since all the lenses G1, G2, G3 of the relay lens system 76B illustrated in FIG. 10 are positive lenses, the image (image plane) of the conjugate plane of the first lens array 73 is curved.
As the weight and size of the liquid crystal projectors have been reduced in recent years, the refracting power of each lens, particularly, in the relay lens system had to be increased and this tended to make the curvature of field greater.
When the image plane is curved, the image is blurred, particularly, only in peripheral portions (four corners) of the illumination area on the liquid crystal display devices, as illustrated in FIG. 11. This will cause nonuniformity of illuminance and thus result in color irregularity of the image projected onto the screen after composition of the three colors, which is not preferable.
An object of the present invention is, therefore, to provide an illumination apparatus and a projection apparatus without nonuniformity of illuminance in the illumination area or with acceptably little nonuniformity of illuminance if any.
An illumination apparatus according to one aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, secondary light source forming means for forming a plurality of secondary light sources from light emitted from the light source means, and a lens system for forming a conjugate plane conjugate with a light entrance plane or a vicinity plane thereof of the secondary light source forming means after a color separation system for separating light from the secondary light source forming means into three beams of mutually different wavelength regions, wherein a relay lens system is placed in a predetermined optical path out of three optical paths of the three beams color-separated and wherein the surface to be illuminated does not agree with a paraxial image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to the above aspect wherein the surface to be illuminated, which does not agree with the paraxial image plane of said conjugate plane formed by said relay lens system, is located while being shifted to the light source side with respect to said paraxial image plane.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, secondary light source forming means for forming a plurality of secondary light sources from light emitted from the light source means, and a lens system for forming a conjugate plane conjugate with a light entrance plane or a vicinity thereof of the secondary light source forming means after a color separation system for separating light from the secondary light source forming means into three beams of mutually different wavelength regions, wherein a relay lens system is placed in a predetermined optical path out of three optical paths of the three beams color-separated and wherein the surface to be illuminated lies at a position shifted from a position of a paraxial image plane to the center side of curvature of an image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects wherein the lens system guides beams from said secondary light sources through a polarizing element for aligning directions of polarization thereof and thereafter guides the beams to said color separation system.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects, which satisfies the following condition:
5.0 less than OAL/L less than 6.0
where OAL is a distance from a first lens unit closest to said light source means in said relay lens system, to the surface to be illuminated, and L is a length of a longitudinal cross section of said surface to be illuminated.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects wherein said relay lens system comprises at least one aspherical lens.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects, which satisfies the following condition:
IMD/L greater than 0.3
where IMD is an equivalent air distance from a final lens surface of said relay lens system to said surface to be illuminated, and L is a length of a longitudinal cross section of the surface to be illuminated.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects wherein a position of an image of said light source means is located at infinity with respect to said surface to be illuminated.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects, wherein said relay lens system comprises a first lens unit G1, a second lens unit G2 spaced through a large aerial gap from said first lens unit G1, and a third lens unit G3 in the stated order from the side of said light source means, said two lens units G1 and G3 of the relay lens system satisfying the following condition:
0.9 less than PW1/PW3 less than 1.3
where PW1 and PW3 are refracting powers of the first lens unit G1 and the third lens unit G3, respectively.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, a rod integrator for taking in light from the light source means and emitting the light, and a lens system for forming a conjugate plane conjugate with a light exit plane or a vicinity plane thereof of the rod integrator after a color separation system for separating the light into three beams of mutually different wavelength regions, wherein a relay lens system is placed in a predetermined optical path out of three optical paths of the three beams color-separated, and wherein the surface to be illuminated does not agree with a paraxial image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to the above aspect, which has the above rod integrator, wherein the surface to be illuminated, which does not agree with the paraxial image plane of said conjugate plane formed by the relay lens system, is located while being shifted to the light source side with respect to said paraxial image plane.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, a rod integrator for taking in light from the light source means and emitting the light, and a lens system for forming a conjugate plane conjugate with a light exit plane or a vicinity plane thereof of the rod integrator after a color separation system for separating the light into three beams of mutually different wavelength regions, wherein a relay lens system is placed in a predetermined optical path out of three optical paths of the three beams color-separated, and wherein the surface to be illuminated lies (at a position shifted from a position of a paraxial image plane) on the center side of curvature of an image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects wherein the lens system guides beams from said rod integrator through a polarizing element for aligning directions of polarization thereof and thereafter guides the beams to said color separation system.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects, which satisfies the following condition:
5.0 less than OAL/L less than 6.0
where OAL is a distance from a first lens unit closes to said light source means in said relay lens system, to the surface to be illuminated, and L is a length of a longitudinal cross section of said surface to be illuminated.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects, wherein said relay lens system comprises at least one aspherical lens.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of the above aspects, which satisfies the following condition:
IMD/L greater than 0.3
where IMD is an equivalent air distance from a final lens surface of said relay lens system to said surface to be illuminated, and L is a length of a longitudinal cross section of the surface to be illuminated.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of above aspects wherein a position of an image of said light source means is located at infinity with respect to said surface to be illuminated.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to either one of above aspects wherein said relay lens system comprises a first lens unit G1, a second lens unit G2 spaced through a large aerial gap from said first lens unit G1, and a third lens unit G3 in the stated order from the side of said light source means, said two lens units G1 and G3 of the relay lens system satisfying the following condition:
0.9 less than PW1/PW3 less than 1.3
where PW1 and PW3 are refracting powers of the first lens unit G1 and the third lens unit G3, respectively.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, secondary light source forming means for forming a plurality of secondary light sources from light emitted from the light source means, and a lens system for forming a conjugate plane conjugate with a light entrance plane or a vicinity plane thereof of the secondary light source forming means, wherein a relay lens system is placed in an optical path and wherein the surface to be illuminated does not agree with a paraxial image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, secondary light source forming means for forming a plurality of secondary light sources from light emitted from the light source means, and a lens system for forming a conjugate plane conjugate with a light entrance plane or a vicinity plane thereof of the secondary light source forming means, wherein a relay lens system is placed in an optical path and wherein the surface to be illuminated is located at a position shifted from a position of a paraxial image plane to the center side of curvature of an image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, a rod integrator for taking in light from the light source means and emitting the light, and a lens system for forming a conjugate plane conjugate with a light exit plane or a vicinity plane thereof of the rod integrator, wherein a relay lens system is placed in an optical path and wherein the surface to be illuminated does not agree with a paraxial image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus for illuminating a surface to be illuminated, by use of light source means, a rod integrator for taking in light from the light source means and emitting the light, and a lens system for forming a conjugate plane conjugate with a light exit plane or a vicinity plane thereof of the rod integrator, wherein a relay lens system is placed in an optical path and wherein the surface to be illuminated is located at a position shifted from a position of a paraxial image plane to the center side of curvature of an image plane of the conjugate plane formed by the relay lens system.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to the above aspect wherein the surface to be illuminated, which does not agree with the paraxial image plane of said conjugate plane of the exit plane of the rod integrator formed by said lens system, is located while being shifted to the light source side with respect to said paraxial image plane.
An illumination apparatus according to another aspect of the present invention is an illumination apparatus comprising:
a first optical system for forming a plurality of secondary light sources from light emitted from a light source; and
a second optical system for illuminating a surface to be illuminated, with a plurality of beams from said plurality of secondary light sources,
wherein said first optical system comprises an optical unit and/or a rod integrator, said optical unit comprising a first lens array placed on the light source side and a second lens array placed on the surface-to-be-illuminated side,
wherein said second optical system projects onto said surface to be illuminated, an image of a light entrance plane of said first lens array or a light exit plane of said rod integrator, or a plane close to either one of said planes, and wherein said image is curved and a position of a paraxial (on-axis) portion of said curved image is shifted from a position of said surface to be illuminated.
An illumination apparatus according to another aspect of the present invention is the illumination apparatus according to the above aspect wherein said image is curved so that an off-axis portion thereof lies closer to said light source than said paraxial portion and wherein the position of said surface to be illuminated is shifted from the position of said paraxial portion toward the light source side.
A projection apparatus according to the present invention is a projection apparatus comprising a liquid crystal display device illuminated by the illumination apparatus as set forth in either one of the above aspects, and a projection optical system for projecting an image formed by said liquid crystal display device.